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Abstract:

Provided herein are etching, cleaning and drying methods using a
supercritical fluid, and a chamber system for conducting the same. The
etching method includes etching the material layer using a supercritical
carbon dioxide in which an etching chemical is dissolved, and removing an
etching by-product created from a reaction between the material layer and
the etching chemical using a supercritical carbon dioxide in which a
cleaning chemical is dissolved. Methods of manufacturing a semiconductor
device are also provided.

Claims:

1. A chamber system comprising: a process chamber into which a
semiconductor substrate having a material layer formed thereon is loaded;
a supplying unit supplying a fluid comprising a solvent in a
supercritical state to the process chamber; a discharging unit
discharging a used fluid from the process chamber; and a controller unit
which controls operations, temperatures and/or pressures of the process
chamber, the supplying unit and/or the discharging unit, wherein the
controller unit maintains the process chamber at a condition above a
critical temperature and/or pressure of the solvent during the treating
step.

2. The chamber system of claim 1, wherein the supercritical fluid
comprises a supercritical carbon dioxide and further comprises an
additional chemical comprises a fluoride, a pyridine (C5H5N),
F-AOT, a fluorine-based surfactant, an alcohol, and combinations thereof.

3. The chamber system of claim 2, wherein the supplying unit comprises:
at least one container in which the carbon dioxide and the additional
chemical are stored separately; and a mixer disposed between the
containers and the process chamber for mixing the supercritical carbon
dioxide and the additional chemical prior to entry into the process
chamber.

4. The chamber system of claim 2, wherein the additional chemical
comprises a block co-polymer to which is chemically bonded a
fluorine-based ionic or non-ionic compound, a hydrophilic compound or a
hydrophobic fluorine-based polymer compound.

5. The chamber system of claim 2, wherein the additional chemical is
PEO-block-PFOMA (polyethylene oxide-block-polyfluorooctyl methacrylate).

6. The chamber system of claim 2, wherein the discharging unit comprises
a separator for selectively separating the supercritical carbon dioxide
and the additional chemical.

7. The chamber system of claim 1, wherein the process chamber comprises a
temperature control unit for controlling a temperature inside the process
chamber and/or a pressure control unit for controlling a pressure inside
the process chamber.

8. The chamber system of claim 3, further comprising: at least one
circulation structure disposed between the mixer and the process chamber
to circulate the supercritical fluid; and a circulation pump disposed on
the circulation structure.

9. The chamber system of claim 8, further comprising a vent portion
disposed on the circulation structure to discharge a portion of the
supercritical fluid.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional application of co-pending U.S.
application Ser. No. 11/752,834 filed May 23, 2007, which claims priority
to Korean Patent Application Nos. 2006-046667, filed on May 24, 2006, and
2007-001514, filed on Jan. 5, 2007, the disclosures of which are each
hereby incorporated by reference herein in their entireties.

FIELD OF THE INVENTION

[0002] The invention provided herein relates to methods for processing a
thin film using supercritical fluids and systems using these methods.

BACKGROUND

[0003] In general, a material is in one of a solid, liquid or gaseous
state according to the temperature and pressure. For example, as pressure
increases under a constant temperature, gas can be generally liquefied.
However, above a critical temperature and pressure, a material can be in
the supercritical state, and the material may not be liquefied regardless
of a further increase of pressure. In a phase diagram, the minimum
temperature and pressure from which the supercritical state starts is
generally referred to as the "critical point."

[0004] When carbon dioxide (CO2), for example, is fed into a closed
container and heated to a temperature and pressure exceeding the critical
point, in general, the boundary between gas and liquid disappears. Unlike
the properties of a typical liquid solvent, the physical properties of a
material in the supercritical state (hereinafter referred to as
"supercritical fluid"), for example, density, viscosity, diffusion
coefficient, polarity and the like, can be continuously changed from
gas-like to liquid-like as the pressure is varied.

[0005] Supercritical fluid may have a high dissolution, a high diffusion
coefficient, low viscosity and low surface tension. Therefore, as a
method for overcoming technical problems related with the efficiency,
quality, reaction rate and environment in a typical process (such as
reaction, decomposition, extraction, distillation, crystallization,
absorption, adsorption, drying and cleaning), technologies employing
supercritical fluid can be used. Carbon dioxide may be a particularly
useful material for, e.g., a process of manufacturing a capacitor
constituting a memory cell of a dynamic random access memory (DRAM),
because, at least in part, it has a critical temperature of 31° C.
and a critical pressure of 73 atm, and is also generally nontoxic,
nonflammable and inexpensive. For instance, Korean Patent Laid Open
Publication No. 2005-0074844 discusses a method of manufacturing a
microelectronic device including removing a thin film using supercritical
carbon dioxide as a solvent. Hereinafter, a process of manufacturing a
capacitor using a conventional method and a problem caused, at least in
part, by the process will be described with reference to FIGS. 2 and 3.
More specifically, FIG. 2 is a sectional view of memory cells of a
conventional DRAM device, and FIG. 3 is a process flow diagram
illustrating a method of manufacturing a DRAM device according to the
related art.

[0006] Again referring to FIGS. 2 and 3, a lower structure 20 is formed on
a semiconductor substrate 10 (S1). The lower structure 20 includes
transistors 30, interconnection line structures 40 connecting the
transistors 30, and an interlayer insulating layer 50 disposed between
the transistors 30 and the interconnection line structures 40. Each of
the transistors 30 includes a gate electrode 31 disposed on the
semiconductor substrate 10, and impurity regions 32 formed in the
semiconductor substrate 10 at both sides of the gate electrode 31. Each
of the interconnection line structures 40 include a lower plug 41, an
interconnection line layer 42 on the lower plug 41, and an upper plug 43
on the interconnection line layer 42. Also, the interlayer insulating
layer 50 includes a lower interlayer insulating layer 51 and an upper
interlayer insulating layer 52, which are sequentially stacked.

[0007] Thereafter, a first sacrificial layer 60 is formed on the lower
structure 20 and is patterned to form openings 65 which expose the upper
plugs 43 (S2). The first sacrificial layer 60 typically includes silicon
oxide, and the upper interlayer insulating layer 52 includes a material
that provides an etch selectivity for the first sacrificial layer 60.
Owing to the etch selectivity, the openings 65 can be formed with a large
aspect ratio (h/w), as shown in the drawing, with no or minimal damage to
the lower structure 20.

[0008] Next, a lower electrode layer is formed in the openings 65, and
then a second sacrificial layer 80 fills the openings 65 on which the
lower electrode layer was formed. The second sacrificial layer 80
generally includes silicon oxide. Thereafter, the second sacrificial
layer 80 and the lower electrode layer are etched until an upper surface
of the first sacrificial layer 60 is exposed. As a result, the lower
electrodes 70 of a capacitor constituting a memory cell of a DRAM device
may be formed (S3) as shown in FIG. 2.

[0009] According to methods known in the art, the first and second
sacrificial layers 60 and 80 are removed by a wet etch to expose the
sidewalls of the lower electrodes 70 (S4). Thereafter, the resultant
structure is cleaned using a cleaning solution to remove by-products
generated in the etching process (S5). However, because the etching
solution or cleaning solution used in these processes can have a surface
tension of a few tens of dynes/cm, the flow of the etching solution or
cleaning solution can cause the lower electrodes 70 having the large
aspect ratio to lean.

[0010] In experiments etching silicon oxide using an etchant including a
supercritical carbon dioxide as a solvent, and hydrofluoric acid (HF) and
pyridine as etching chemicals, as shown in FIGS. 8A and 8B, it was found
that etching by-products are generated from the HF and pyridine, which
can be removed using de-ionized water. However, this cleaning can cause
the lower electrode to lean. Therefore, methods are needed to prevent the
leaning of the lower electrodes in this process.

SUMMARY OF THE INVENTION

[0011] Embodiments of the present invention provide methods of etching and
cleaning a material layer including etching the material layer with a
supercritical carbon dioxide which further includes an etching chemical;
and removing an etching by-product created from a reaction between the
material layer and the etching chemical with a supercritical carbon
dioxide which further includes a cleaning chemical.

[0012] Embodiments of the present invention also provide methods of
manufacturing a semiconductor device including forming conductive
patterns and a silicon oxide layer disposed around the conductive
patterns on a semiconductor substrate; selectively etching the silicon
oxide layer using a supercritical carbon dioxide further including
fluoride, pyridine (C5H5N), or combinations thereof; and
removing an etching by-product generated in the etching using a
supercritical carbon dioxide further including F-AOT, fluorine-based
surfactants, alcohol, or combinations thereof.

[0013] Embodiments of the present invention further provide chamber
systems that perform methods of treating a semiconductor substrate with a
supercritical fluid, the chamber system including a process chamber into
which a semiconductor substrate having a material layer formed thereon is
loaded; a supplying unit supplying a fluid including a solvent in a
supercritical state to the process chamber; a discharging unit
discharging the used fluid from the process chamber; and a controller
that controls operations, temperatures and/or pressures of the process
chamber, the supplying unit and the discharging unit, wherein the
controller maintains the process chamber at a condition above a critical
temperature and/or pressure of the solvent during the treatment.

[0014] Embodiments of the present invention also provide methods of drying
a water-soluble chemical including treating a material layer with the
water-soluble chemical; and removing the water-soluble chemical using a
supercritical fluid including a supercritical carbon dioxide and further
including a surfactant.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above aspects of the present invention will become more
apparent by describing in detail various embodiments thereof with
reference to the attached drawings in which:

[0024] FIGS. 9A and 9B present process flow diagrams illustrating methods
of manufacturing a DRAM device using etching and cleaning processes
according to some embodiments of the present invention.

[0025] FIG. 10 presents a process flow diagram illustrating a cleaning
process according to further embodiments of the present invention.

[0026] FIG. 11 presents photographs of a DRAM device formed according to
some embodiments of the present invention. P1 shows a first resultant
structure in which the lower electrodes (70) are formed. P2 shows a
second resultant structure obtained by etching the first resultant
structure prior to cleaning. Etching by-products (99) are found on the
surfaces of the lower electrodes (70). P3 shows a third resultant
structure after cleaning. The surfaces of the lower electrodes (70) are
exposed and cleaned without causing the electrodes to lean.

[0027] FIG. 12 presents a device scheme of a chamber system for etching
and cleaning processes according to some embodiments of the present
invention.

[0028] FIG. 13 presents a device scheme of a chamber system according to
other embodiments of the present invention.

[0029] FIG. 14 presents a process flow diagram for illustrating a drying
process according to further embodiments of the present invention.

DETAILED DESCRIPTION

[0030] The present invention will now be described more fully with
reference to the accompanying drawings, in which exemplary embodiments of
the invention are shown. The invention may, however, be embodied in many
different forms and should not be construed as being limited to the
embodiments set forth herein; rather, these embodiments are provided so
that this disclosure will be thorough and complete, and will fully convey
the concept of the invention to those skilled in the art.

[0031] In the drawings, the size and relative sizes of layers and regions
may be exaggerated for clarity. The drawings are not necessarily to
scale. Like reference numerals designate like elements throughout the
drawings.

[0032] It will also be understood that when an element or layer is
referred to as being "on," "connected to" and/or "coupled to" another
element or layer, the element or layer may be directly on, connected
and/or coupled to the other element or layer or intervening elements or
layers may be present. In contrast, when an element is referred to as
being "directly on," "directly connected to" and/or "directly coupled to"
another element or layer, no intervening elements or layers are present.

[0033] As used herein, the term "and/or" may include any and all
combinations of one or more of the associated listed items and may be
abbreviated as "/".

[0034] It will also be understood that, although the terms first, second,
etc. may be used herein to describe various elements, components,
regions, layers and/or sections. These elements, components, regions,
layers and/or sections should not be limited by these terms. These terms
may be used to distinguish one element, component, region, layer and/or
section from another element, component, region, layer and/or section.
For example, a first element, component, region, layer and/or section
discussed below could be termed a second element, component, region,
layer and/or section without departing from the teachings of the present
invention.

[0035] Spatially relative teens, such as "beneath," "below," "lower,"
"above," "upper" and the like may be used to describe an element and/or
feature's relationship to another element(s) and/or feature(s) as, for
example, illustrated in the figures. It will be understood that the
spatially relative terms are intended to encompass different orientations
of the device in use and/or operation in addition to the orientation
depicted in the figures. For example, if the device in the figures is
turned over, elements described as "below" and/or "beneath" other
elements or features would then be oriented "above" the other elements or
features. The device may be otherwise oriented (e.g., rotated 90 degrees
or at other orientations) and the spatially relative descriptors used
herein interpreted accordingly.

[0036] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of the
invention. As used herein, the singular terms "a," "an" and "the" are
intended to include the plural forms as well, unless the context clearly
indicates otherwise. For example, "a" polymer layer can mean more than
one polymer layer unless a single layer is specifically noted. It will be
further understood that the terms "includes" and/or "including," when
used in this specification, specify the presence of stated features,
integers, steps, operations, elements, and/or components, but do not
preclude the presence and/or addition of one or more other features,
integers, steps, operations, elements, components, and/or groups thereof.

[0037] Unless otherwise defined, all terms (including technical and
scientific terms) used herein may have the same meaning as what is
commonly understood by one of ordinary skill in the art. It will be
further understood that terms, such as those defined in commonly used
dictionaries, should be interpreted as having a meaning that is
consistent with their meaning in the context of this specification and
the relevant art and will not be interpreted in an idealized and/or
overly formal sense unless expressly so defined herein. Further, all
publications, patent applications, patents, and other references
mentioned herein are incorporated by reference in their entirety.

[0038] Embodiments of the present invention are described with reference
to plan views and cross-sectional illustrations that are schematic
illustrations of idealized embodiments of the present invention. As such,
variations from the shapes of the illustrations as a result, for example,
of manufacturing techniques and/or tolerances, are to be expected. Thus,
embodiments of the present invention should not be construed as limited
to the particular shapes of regions illustrated herein but are to include
deviations in shapes that result, for example, from manufacturing. For
example, a region illustrated as a rectangle will, typically, have
rounded or curved features. Thus, the regions illustrated in the figures
are schematic in nature of a device and are not intended to limit the
scope of the present invention.

[0039] FIGS. 4A and 4B present process flow diagrams illustrating methods
for etching and cleaning a material layer according to some embodiments
of the present invention. Referring to FIG. 4A, a material layer is
formed on a substrate (S10). The material layer is etched using a
supercritical carbon dioxide (CO2) in which an etching chemical is
dissolved (S11), and then an etching by-product generated by a reaction
between the material layer and the etching chemical is removed (S12).

[0040] According to some embodiments, the material layer may include a
silicon oxide, e.g., tetraethylorthosilicate (TEOS) or
borophosphosilicate glass (BPSG).

[0042] In some embodiments, the cleaning chemical includes sodium
bis(2,2,3,3,4,4,5,5-octafluoro-1-pentyl)-2-sulfosuccinate (F-AOT),
fluorine-based surfactants, alcohol, or combinations thereof. Examples of
fluorine-based surfactants include, but are not limited to, those having
a structure of RfCH2CH2SCH2CH2CO2Li,
(RfCH2CH2O)P(O)(ONH4)2
(RfCH2CH2O)2P(O)(ONH4),
(RfCH2CH2O)P(O)(OH)2
(RfCH2CH2O)2P(O)(OH),
RfCH2CH2O(CH2CH2O)xH,
RfCH2CH2O(CH2CH2O)yH,
RfCH2CH2O(CH2CH2O)yH and
RfCH2CH2SO3X (wherein X═H or NH4,
Rf═CF3(CF2)q or CF3(CF2O)q, x=2 to
50, y=2 to 50, q=2 to 50). Examples of these surfactants include, but are
not limited to, ZONYL®-FSA, ZONYL®-FSP, ZONYL®-FSE,
ZONYL®-UR, ZONYL®-FSJ, ZONYL®-TBS, ZONYL®-FSN,
ZONYL®-FSO, ZONYL®-FSD, and the like, manufactured by E.I. du
Pont de Nemours and Company, U.S.A. Examples of suitable alcohols for the
cleaning chemical include, but are not limited to, methanol, ethanol,
isopropanol (IPA), propanol, and combinations thereof.

[0043] According to another embodiment of the present invention, as shown
in FIG. 4B, the step of etching the material layer and the step of
removing the etching by-product can be performed simultaneously (S13). In
some embodiments, a supercritical carbon dioxide in which the etching
chemical and the cleaning chemical are dissolved together is used for the
etching and cleaning.

[0044] Furthermore, the aforementioned method using the supercritical
carbon dioxide can be employed to etch and/or clean another type of
material layer. The etching chemical and the cleaning chemical used for
this purpose can be changed depending on the target material layer used.

[0045] FIGS. 5A and 5B present experimental graphs showing results of the
etch rate measured by etching methods according to the present invention.
Specifically, FIGS. 5A and 5B present graphs showing etch rates measured
on a BPSG layer and a TEOS layer respectively formed at a thickness of
approximately 8500 Å on bare wafers. The etching chemicals used in
the above experiments was a solution in which HF and pyridine were mixed
at a volume ratio of 7:3. That is, the same etching chemical was used for
the experiments. In the experiments, the etchings for the BPSG layer and
the TEOS layer were performed at 70° C. using a solution in which
the prepared etching chemical and a solvent were mixed at a volume ratio
of 1:100. In the first experiment, supercritical carbon dioxide was used
as the solvent, whereas in the second and third experiments
(corresponding to the related art methods), de-ionized water and pyridine
were used as the solvent.

[0046] Referring to FIG. 5A, it can be found that using supercritical
carbon dioxide shows a three (3) to six (6) times faster etch rate than
the methods using the de-ionized water and the pyridine. Also, in the
etching experiment using the supercritical carbon dioxide, the etched
amounts in the process times of 5 minutes and 10 minutes were almost
identical.

[0047] Referring to FIG. 5B, it is demonstrated that the etching method
using supercritical carbon dioxide etched the TEOS layer at a faster rate
than the methods using the de-ionized water and the pyridine. The
improvement in the etch rate is due, at least in part, to an increase in
reaction speed obtainable because the CO2 used as the solvent is in
the supercritical state.

[0048] FIGS. 6A and 6B present graphs showing experimental results for
evaluating a temperature condition in an etching process according to
embodiments of the present invention. Specifically, FIGS. 6A and 6B
present graphs showing the etch rates of a BPSG layer and a TEOS layer,
respectively, measured at a fixed pressure of 2000 psi for 5 minutes at
temperatures of 33, 50 and 70° C. The etching chemicals used in
this experiment are the same as those used in the experiment described
above with reference to FIGS. 5A and 5B.

[0049] Referring to FIGS. 6A and 6B, the etch rates of the BPSG layer and
the TEOS layer increased as the process temperature was increased.
Accordingly, the temperature range for the etching process in some
embodiments of the present invention may be from about 31.1° C.
(which is generally a critical temperature of CO2) to about
100° C. Although not shown in the drawings, the etch rate at a
process temperature above 70° C. was not particularly increased
compared with the etch rate at 70° C. Therefore, in further
embodiments, the temperature range for the etching process is from about
50° C. to 70° C.

[0050] FIGS. 7A and 7B present graphs showing experimental results for
evaluating the effects of pressure in an etching process according to
some embodiments of the present invention. Specifically, FIGS. 7A and 7B
present are graphs showing the etch rates of a BPSG layer and a TEOS
layer, respectively, measured at pressures of 1500, 2000 and 3000 psi for
5 minutes at a temperature of 70° C. The etching chemicals used in
these experiments are the same as those used in the experiments described
above with reference to FIGS. 5A and 5B.

[0051] Referring to FIGS. 7A and 7B, it was found that the BPSG layer and
the TEOS layer had the highest etch rate at a pressure of approximately
2000 psi. In this respect, in some embodiments, the pressure for the
etching process is in a range of 1500 psi to 2500 psi. Alternatively, the
pressure may be in a range of 1085 psi (which is a critical pressure of
carbon dioxide) to 4000 psi.

[0052] In some embodiments, the aforementioned etching method of the
present invention can be used for a process of manufacturing a capacitor
constituting a unit cell of a DRAM device. As shown in FIGS. 8A and 8B,
after the etching step, etching by-products, which are presumed to be
generated from a reaction between the etching chemicals and the silicon
oxide, may be left on a substrate (or bare substrate). These etching
by-products can be removed by a cleaning solution that includes
de-ionized water. However, as previously described, because this cleaning
solution causes these capacitors having a large aspect ratio to lean, its
use is limited. The cleaning method according to some embodiments of the
present invention provides a solution to the leaning problem by making
use of compositions that include a supercritical solvent.

[0053] FIGS. 9A and 9B present flow diagrams illustrating methods of
manufacturing a DRAM capacitor using etching and cleaning processes
according to some embodiments of the present invention. The methods
illustrated in FIGS. 9A and 9B are the same as the aforementioned method
illustrated with reference to FIG. 2, except for the steps of etching and
cleaning the sacrificial layers 60 and 80, and therefore, repeated
description of similar steps will be omitted for simplicity of
discussion.

[0054] Referring to FIGS. 2 and 9A, a lower structure 20 is formed on a
semiconductor substrate 10 (S20), and then a first sacrificial layer 60
having openings 65 is formed on the lower structure 20 (S21). The lower
electrode 70 is then formed by using the openings 65 as a mold (S22). In
some embodiments, the openings 65 on which the lower electrode 70 is
formed can be filled with a second sacrificial layer 80.

[0055] Thereafter, in some embodiments, the first and second sacrificial
layers 60 and 80 are selectively etched using a supercritical carbon
dioxide in which etching chemicals are dissolved (S23). In further
embodiments, etching by-products generated from a reaction between the
first and second sacrificial layers 60 and 80 and the etching chemicals
can be removed using a supercritical carbon dioxide in which cleaning
chemicals is dissolved (S24).

[0056] According to some embodiments of the present invention, the first
and second sacrificial layers 60 and 80 are silicon oxides. Examples of
suitable silicon oxides include, but are not limited to,
tetraethylorthosilicate (TEOS), borophosphosilicate glass (BPSG),
spin-on-glass (SOG), and combinations thereof. In some embodiments, the
etching chemicals include fluoride, pyridine (C5H5N), or
mixtures thereof, and the cleaning chemicals include F-AOT (sodium
bis(2,2,3,3,4,4,5,5-octafluoro-1-pentyl)-2-sulfosuccinate),
fluorine-based surfactants alcohol, or mixtures thereof.

[0057] In some embodiments, the fluoride used for the etching chemical may
be at least one of hydrofluoric acid (HF), hydrofluoroether (HFE),
poly[4-vinylpyridinium poly(hydrogen fluoride)], hydrogen fluoride
2,4,6-trimethylpyridine or ammonium fluoride (NH4F). Also, in
further embodiments, the surfactant for the etching chemicals may include
a block copolymer to which a compound is bonded, e.g., fluorine-based
ionic or non-ionic compounds, hydrophilic compounds, hydrophobic
fluorine-based polymer compounds, or mixtures/combinations thereof. In
some embodiments, the fluorine-based ionic or non-ionic compounds may be
materials having a chemical structure of
RfCH2CH2SCH2CH2CO2Li,
(RfCH2CH2O)P(O)(ONH4)2
(RfCH2CH2O)2P(O)(ONH4),
(RfCH2CH2O-)P(O)(OH)2
(RfCH2CH2O)2P(O)(OH),
RfCH2CH2O(CH2CH2O)xH,
RfCH2CH2O(CH2CH2O)yH,
RfCH2CH2O(CH2CH2O)yH or
RfCH2CH2SO3X (wherein X═H or NH4,
Rf═CF3(CF2)q or CF3(CF2O)q, x=2 to
50, y=2 to 50, q=2 to 50). These may be fluorine-based surfactants
manufactured by E.I. du Pont de Nemours and Company, U.S.A. (ZONYL®).
Also, in some embodiments the hydrophilic compound may be at least one
selected from the group consisting of a polyethylene oxide (PEO) chain
and polypropylene oxide (PPO), and the hydrophobic fluorine-based polymer
compound may be poly(fluorooctyl methacrylates) (PFOMA). According to an
embodiment of the present invention, the fluoride for the etching
chemicals may be a fluorine-based block copolymer one example of which
may be PEO-block-PFOMA (polyethylene oxide-block-poly(fluorooctyl
methacrylate) (poly(ethylene oxide)-b-poly(1,1'-dihydroperflurooctyl
methacrylate) shown below in Formula 1. In addition, in some embodiments,
the fluoride for the etching chemicals may be a block copolymer to which
the hydrophilic PEO and the hydrophobic PFOMA are bonded in AB or ABA
structure. In some embodiments, A may be PEO and B may be PFOMA.

##STR00001##

where Rf═CF3(CF2)q or CF3(CF2O)q,
m=2 to 50, n=2 to 50, q=2 to 50.

[0058] In some embodiments, the fluorine-based surfactants that may be
used as the cleaning chemicals may be materials having a chemical
structure of RfCH2CH2SCH2CH2CO2Li,
(RfCH2CH2O)P(O)(ONH4)2
(RfCH2CH2O)2P(O)(ONH4),
(RfCH2CH2O)P(O)(OH)2
(RfCH2CH2O)2P(O)(OH),
RfCH2CH2O(CH2CH2O)xH,
RfCH2CH2O(CH2CH2O)yH,
RfCH2CH2O(CH2CH2O)yH or
RfCH2CH2SO3X (X═H or NH4,
Rf═CF3(CF2)q or CF3(CF2O)q, x=2 to
50, y=2 to 50, q=2 to 50). These may be fluorine-based surfactants
manufactured by E. I. du Pont de Nemours and Company, U.S.A.
(ZONYL®). According to another embodiment of the present invention,
the fluorine-based surfactant for use as the cleaning chemicals may be a
block copolymer, for example, PEO-block-PFOMA (polyethylene
oxide-block-poly fluorooctyl methacrylate) (Formula 1) to which
hydrophilic compounds and/or hydrophobic fluorine-based polymer compounds
are chemically bonded. Examples of alcohol used for the cleaning chemical
include, but are not limited to, methanol, ethanol, isopropanol (IPA),
propanol, and combinations thereof.

[0059] As aforementioned, in some embodiments, the etching and cleaning
steps (S23, S24) are performed at a temperature of about 70° C.
and at a pressure of about 2000 psi. Also, in further embodiments, the
etching chemicals are dissolved in the supercritical carbon dioxide in an
amount of about 0.01% by weight to 10% by weight.

[0060] In some embodiments, after the cleaning step (S23) is performed, a
step of drying a structure resulting from the cleaning step (S23) may be
performed. The drying step can include a step of lowering the temperature
of a process chamber into which the cleaned resultant structure is loaded
to a temperature below the critical point of carbon dioxide. In this
case, the supercritical carbon dioxide can be discharged in a gas state
to the outside of the process chamber.

[0061] According to further embodiments of the present invention, the
cleaning step (S24) can be divided into a first cleaning step (S241) and
a second cleaning step (S242) as shown in FIG. 10. In the first cleaning
step (S241), de-ionized (DI) water and F-AOT (Formula 2) may be used as
the cleaning chemicals, and the second cleaning step (S242) may use only
the supercritical carbon dioxide. In some embodiments, the ratios by
weight of the DI water and the F-AOT used in the first cleaning step
(S241) are in the range of about 0.01 wt % to 5 wt % and about 0.01 wt %
to 10 wt %. In some embodiments, the DI water used in the first cleaning
step (S241) is bonded to F-AOT to at least increase the efficiency of
cleaning to remove the etching by-products.

##STR00002##

[0062] According to another embodiment of the present invention, an
intermediate cleaning step (S24) including alcohol as a cleaning chemical
can be further performed between the first and second cleaning steps
(S241 and S242). Examples of alcohols used in the intermediate cleaning
step (S243) include, but are not limited to, ethanol, isopropanol (IPA),
propanol, and mixtures thereof, and in some embodiments the alcohol is
provided in a ratio by weight ranging from 0.01 wt % to 50 wt %.

[0063] According to another embodiment of the present invention, the
etching step (S23) and the cleaning step (S24) can be performed
simultaneously using a supercritical carbon dioxide in which the
aforementioned etching chemical and the cleaning chemical are dissolved
together (S25).

[0064] The photographs presented in FIG. 11 show the results of the
aforementioned cleaning process according to some embodiments of the
present invention. Referring to FIG. 11, the left photograph (P1) shows a
resultant structure (hereinafter referred to as "first resultant
structure") in which the lower electrodes 70 are formed, and the middle
photograph (P2) shows a resultant structure (hereinafter referred to as
"second resultant structure") obtained by etching the first resultant
structure using some embodiments of the aforementioned etching method.
The middle photograph (P2) corresponds to a photograph of a resultant
structure before the cleaning process according to some embodiments of
the present invention is performed. As shown in the photograph, etching
by-products 99 can be found on surfaces of the lower electrodes.

[0065] The right photograph (P3) shows a resultant structure (hereinafter
referred to as "third resultant structure") after the cleaning process is
performed according to some embodiments of the present invention. As
shown in the right photograph, the etching by-products 99 have been
removed from the surfaces of the lower electrodes 70. Also, due, at least
in part, to the low surface tension of the aforementioned compositions
including supercritical carbon dioxide, the surfaces of the lower
electrodes 70 are exposed with no or minimal leaning problem of the lower
electrodes 70.

[0066] FIG. 12 presents a device scheme of a chamber system for etching
and cleaning processes according to some embodiments of the present
invention. Referring to FIG. 12, a chamber system according to some
embodiments of the present invention includes a process chamber 300, a
supplying unit 320 and a discharging unit 340. A substrate on which a
material layer is formed is loaded into the process chamber 300. The
supplying unit 320 supplies the process chamber 300 with etching fluid
for etching the material layer and/or cleaning fluid for removing etching
by-products in a supercritical state. The discharging unit 340 discharges
the etching fluid and the cleaning fluid used from the process chamber
300 to the outside of the process chamber 300. In some embodiments, the
etching fluid and the cleaning fluid include etching chemicals and
cleaning chemicals that are dissolved in a supercritical solvent, and in
some embodiments, the supercritical solvent is carbon dioxide.

[0067] According to further embodiments of the present invention, while
the step of etching the material layer and the step of removing the
etching by-products are performed, the process chamber 300 is kept at a
temperature above the critical temperature and at a pressure above the
critical pressure. Therefore, the etching step and the cleaning step can
be successively performed while maintaining the supercritical state of
the solvent.

[0068] In some embodiments, the supplying unit 320 is provided with a
first container 321 containing a solvent, and second and third containers
322 and 323 containing a co-solvent including the etching chemical and
the cleaning chemical. More or fewer containers may be provided as
desired. According to some embodiments of the present invention, the
solvent can be carbon oxide and the etching chemical can be fluoride,
pyridine (C5H5N), or mixtures thereof. Also, in further
embodiments, the cleaning chemical may be F-AOT, fluorine-based
surfactants, de-ionized (DI) water, alcohol, or combinations thereof. In
some embodiments, the etching chemicals and the cleaning chemicals used
may include those described with reference to FIG. 9A.

[0069] According to some embodiments of the present invention, a booster
pump 331 for safely supplying the solvent at a constant flow, and a
temperature controller (e.g., cooler) 332 for easily pressurizing the
solvent are disposed between the first container 321 and the process
chamber 300. A first pressure pump 333 for elevating the pressure of the
solvent above the critical pressure is disposed between the temperature
controller 332 and the process chamber 330, and a mixer 335 for mixing
the solvent with the co-solvent is disposed between the first pressure
pump 333 and the process chamber 300. In some embodiments, the mixer 335
precisely regulates the amount of the fluid introduced into the process
chamber 300.

[0070] For this purpose, the second and third containers 322 and 323 are
connected via a second pipe 312 to the mixer 335. On the second pipe 312,
a second pressure pump 334 for elevating the pressure of the co-solvent
may be disposed as shown in the figure. Also, the booster pump 331, the
temperature controller 332 and the first pressure pump 333 are disposed
on a first pipe 311 connecting the first container 321 and the mixer 335.

[0071] In some embodiments, the etching fluid wherein the solvent and the
etching chemical are mixed is supplied to the mixer 335 and the process
chamber 300 during the etching step, and then the cleaning fluid wherein
the solvent and the cleaning chemical are mixed is supplied during the
cleaning step. This sequential fluid supply is performed while
maintaining the solvent at a temperature and pressure above the critical
point as described above. For this purpose, as shown in the figures, in
some embodiments, valves 351 to 356 for regulating the supplies of the
solvent and the co-solvent can be disposed on the pipes (e.g., first pipe
311 and second pipe 312) connecting the process chamber 300 and the
containers 321 to 323. In addition, for the maintenance of this
condition, a controller (not shown) for controlling the operations of the
valves 351 to 356, the booster pump 331, the temperature controller 332,
the first and second pressure pumps 333 and 334, and the mixer 335 can be
further disposed in some embodiments. The operations of the discharging
unit 340 may also be controlled by the controller.

[0072] In some embodiments, the discharging unit 340 is provided with a
separator 341 for separating a solvent and harmful chemicals (e.g., the
etching chemicals and/or cleaning chemicals) from the fluid discharged
from the process chamber 300. For this separation, a basic material for
neutralizing the etching chemical can be supplied to the separator 341.
In further embodiments, between the separator 341 and the process chamber
300 is further disposed a discharge valve 343 controlled by the
controller. Furthermore, according to some embodiments of the present
invention, a rupture disk 342 can be connected to the process chamber 300
for preventing a pressurized solvent from being abruptly discharged from
the process chamber 300. Meanwhile, for the enhancement of productivity,
in some embodiments, all or parts of the elements mentioned above are
electronically controlled by a controller.

[0073] In some embodiments, the pressure and temperature of the solvent
are kept above the critical point as described above to maintain the
solvent in a supercritical state. In further embodiments, the
above-described chamber system may be provided with a temperature
measuring unit, pressure measuring unit, temperature controlling unit
and/or pressure controlling unit capable of monitoring and/or controlling
the temperature and pressure of the fluid used. For example, in some
embodiments, first to fifth temperature control jackets 361 to 365
controlled by the temperature controlling unit are disposed around a pipe
connected to the mixer 335, a pipe between the process chamber 300 and
the mixer 335, the process chamber 300 and the discharge valve 343.

[0074] According to some embodiments of the present invention, the chamber
system can be utilized for the step of drying a water-soluble chemical as
well as for the steps of etching and cleaning the material layer. In some
embodiments, a common solvent for this purpose is stored in the second
and third containers 322 and 323. The common solvent for drying according
to some embodiments of the present invention will be described below, and
in some embodiments, is similar to that of previous embodiments except
for a difference in the type of chemical.

[0075] FIG. 13 presents a device scheme of a chamber system according to
another embodiment of the present invention. The chamber system shown in
FIG. 13 is similar to that of the embodiments described with reference to
FIG. 12. Accordingly, for the simplicity of description, repeated
description of the overlapping elements will be omitted.

[0076] Referring to FIGS. 12 and 13, the chamber system according to some
embodiments includes a circulation pipe which can circulate a
supercritical fluid between the mixer 335 and the process chamber 300. In
some embodiments, the circulation pipe includes a first circulation pipe
371 which delivers the supercritical fluid prepared in the mixer 335 to
the process chamber, and a second circulation pipe 372 which delivers the
supercritical fluid used in the process chamber 300 to the mixer 335. For
the circulation of this supercritical fluid, in further embodiments, a
circulation pump 375 is further provided on the circulation pipe. The
circulation pump 375 can be disposed on, for example, the first
circulation pipe 371 or the second circulation pipe 372.

[0077] In addition, in some embodiments, a vent portion 376 for
discharging at least a portion of the used supercritical fluid can be
connected, e.g., onto the second circulation pipe 372. Upon discharging
at least a portion of the used supercritical fluid through the vent
portion 376, the supercritical fluid can be additively supplied to the
mixer 335. Therefore, in some embodiments, it is possible to perform a
selected process using the supercritical fluid having a substantially
uniform purity without a substantial pressure variation in the inside of
the process chamber 300.

[0078] FIG. 14 presents a process flow diagram for illustrating a drying
process according to some embodiments of the present invention. Referring
to FIG. 14, the drying step according to some embodiments includes the
step (S30) of forming a material layer, the step (S32) of treating the
material layer with a water-soluble chemical and the step (S34) of
removing the water-soluble chemical using a supercritical fluid.
According to further embodiments of the present invention, the step (S33)
of rinsing the material layer, which has been treated with the
water-soluble chemical, using, e.g., IPA, HFE, or mixtures thereof, may
be further provided before the step (S34) of removing the water-soluble
chemical using a supercritical fluid. In addition, in some embodiments,
the step (S35) of flushing a resultant structure from which the
water-soluble chemical has been removed, using a supercritical carbon
dioxide may be further provided after the step (S34) of removing the
water-soluble chemical using a supercritical fluid.

[0079] According to some embodiments of the present invention, the step
(S32) of treating the material layer may be any one of, e.g., the steps
of etching the material layer using a predetermined etchant, cleaning the
material layer using a predetermined cleaning solution, and pre-cleaning
the material layer using a predetermined cleaning solution before forming
a new layer on the material layer. In some embodiments, the material
layer can be, e.g., a silicon oxide used as a mold layer for forming a
lower capacitor electrode of a DRAM, or a conductive material (e.g., Si,
TiN, Ti, W, Ru, Ir or the like) used as the lower capacitor electrode of
the DRAM. In the case of etching a silicon oxide layer, in some
embodiments, the water-soluble chemical used in the step (S32) of
treating the material layer can be a chemical substance containing
de-ionized (DI) water and fluorine dissolved in DI water.

[0080] In other embodiments, the step (S32) of treating the material layer
includes the step of dipping the resultant structure on which the
material layer is formed into the water-soluble chemical. In further
embodiments, the dipping step includes a drying step of removing the
water-soluble chemical used. However, when the lower capacitor electrode
of the DRAM having a high aspect ratio is dried using a conventional
method, this action may cause a leaning problem, as aforementioned.
However, by employing the drying method provided in the present invention
which removes the water-soluble chemical using the supercritical fluid,
the leaning problem may be overcome with the low viscosity and/or surface
tension of the supercritical fluid.

[0081] In some embodiments, the supercritical fluid used in the step (S34)
of removing the water-soluble chemical can include a supercritical carbon
dioxide and a surfactant. Examples of suitable surfactants include, but
are not limited to, a TMN-based surfactant, a fluorine-based surfactant
having a branch, a surfactant containing a fluorine block copolymer, or
combinations thereof. According to some embodiments of the present
invention, the TMN-based surfactant can be TMN-10, which is expressed by
Formula 3:

##STR00003##

[0082] In some embodiments, the branched fluorine-based surfactant can
include materials having a chemical structure of
RfCH2CH2SCH2CH2CO2Li,
(RfCH2CH2O)P(O)(ONH4)2
(RfCH2CH2O2P(O)(ONH4),
(RfCH2CH2O)P(O)(OH)2
(RfCH2CH2O)2P(O)(OH),
RfCH2CH2O(CH2CH2O)xH,
RfCH2CH2O(CH2CH2O)yH,
RfCH2CH2O(CH2CH2O)yH,
RfCH2CH2SO3X (wherein X═H or NH4,
Rf═CF3(CF2)q or CF3(CF2O)q, x=2 to
50, y=2 to 50, q=2 to 50), or combinations thereof. Alternatively, the
branched fluorine-based surfactant may be F-AOT, which is expressed by
Formula 2. In some embodiments, the surfactant containing the fluorine
block copolymer may be a block copolymer (e.g., PEO-block-PFOMA (Poly
ethylene oxide-block-poly fluorooctyl methacrylate) expressed by Formula
1 to which hydrophilic compounds, hydrophobic fluorine-based polymer
compounds, or mixtures thereof are chemically bonded.

[0083] The PEO-block-PFOMA is non-ionic, is stable in acidic compositions,
and is useful in removing a water-soluble solution in which approximately
120 water molecules are bonded to one surfactant molecule. The drying
characteristics using the supercritical carbon dioxide containing the
PEO-block-PFOMA were tested by the inventors. The experiment was
performed by etching a molded oxide layer to form lower capacitor
electrodes using a buffered oxide etchant (BOE) at 25° C., rinsing
the resultant structure using DI water at 25° C., removing the DI
water using the supercritical carbon dioxide containing the
PEO-block-PFOMA at 40° C., and measuring the amount of the
remaining DI water. The removal efficiency of DI water by the
supercritical carbon dioxide containing the PEO-block-PFOMA approached
approximately 100%, and the supercritical carbon dioxide containing the
PEO-block-PFOMA showed an improved removal effect compared to other known
compounds.

[0084] As described above, the etching and cleaning steps according to
some embodiments of the present invention are performed using a
supercritical fluid. Owing to at least a high reactivity of the
supercritical fluid, the etching process according to some embodiments of
the present invention has an improved efficiency. Also, because, at least
in part, due to the low surface tension of the supercritical fluid, the
etching processes according to some embodiments of the present invention
can prevent the lower electrodes from leaning during a manufacturing
process of a capacitor constituting a memory cell of a DRAM device and
can also remove etching by-products.

[0085] The above-disclosed subject matter is to be considered
illustrative, and not restrictive, and the appended claims are intended
to cover all such modifications, enhancements, and other embodiments,
which fall within the true spirit and scope of the present invention as
defined by the following claims.

Patent applications in class For detection or control of pressure or flow of etchant gas

Patent applications in all subclasses For detection or control of pressure or flow of etchant gas